A systematic review of the relationships between nurse leaders' leadership styles and nurses' work‐related well‐being

Abstract Aim This systematic review aimed to summarize current research knowledge about the relationships between nurse leaders' leadership styles and nurses' work‐related well‐being. Background Due to the global shortage of nurses, it is essential for nurse leaders to maximize staff retention and work‐related well‐being. Methods Following Cochrane Collaboration procedures, the PRISMA statement and PRISMA checklist, relevant quantitative studies published between 1 January 2012 and 31 December 2020 were retrieved from the CINAHL, Scopus, PubMed and Medic databases and then systematically reviewed. Seventeen cross‐sectional and follow‐up studies with surveys were retained for inclusion and evaluated with the Critical Appraisal of a Survey instrument. The data were summarized narratively. Results Three core themes of leadership styles: destructive, supportive and relationally focused, were identified, with statistically significant direct and indirect connections between nurses' work‐related well‐being. Well‐being was mainly assessed in terms of burnout. Effects of leadership styles on work‐related well‐being were reportedly mediated by trust in leader, trust in organization, empowerment, work‐life conflict, relational social capital, emotional exhaustion, affectivity, job satisfaction and motivation. Conclusion Nurse leaders' leadership styles affect nurses' work‐related well‐being. In developing intervention studies and providing training on work‐related well‐being, the impact of the indirect effects and the mediating factors of the leadership styles should be acknowledged.

• Nurse leaders' leadership styles strongly affect the nursing staff, their working environment and work-related well-being.
What this paper adds?
• This systematic review shows that nurse leaders' destructive, supportive and relationally focused leadership styles significantly affect nurses' work-related wellbeing.
• It provides detailed information regarding direct and indirect associations between leadership styles and work-related well-being and the mediating variables for indirect associations.
• The data suggest that nurse leaders should be capable of using supportive and relationally focused leadership styles.
The implications of this paper • Systematic evaluation of nurse leaders' leadership styles in organizations is important because they significantly affect nurses' work-related well-being.
• Results of this review could be used when developing nurse leaders' leadership styles and work environments and planning and implementing leadership training.
• In the developing of intervention studies on work-related well-being, the results of the indirect effects and the mediating factors of the leadership styles should be acknowledged.

| INTRODUCTION
The worldwide shortage of nurses (Chan et al., 2013;Heinen et al., 2013; WHO, 2016) poses a major challenge for leadership in nursing.
Nurses who stay in their profession, work efficiently and produce good patient outcomes, have also generally high work-related wellbeing (Long, 2020;Nantsupawat et al., 2016;Van Bogaert et al., 2014). Several reviews (Cummings et al., 2018;Skakon et al., 2010;Weberg, 2010) rooted in different disciplines have found that managers' use of certain leadership styles can enhance relationships with employees, performance, productivity, the working environment and work-related well-being. Conversely, inappropriate leadership increases costs, employee turnover and absenteeism while reducing performance.
Leaders' well-being affects that of their subordinates (Skakon et al., 2010). However, previous reviews (Awa et al., 2010;Van Wyk & Pillay-Van Wyk, 2010;Westermann et al., 2014) indicate that this relationship is poorly studied. Most interventions targeting nurses' and nurse leaders' work-related well-being are focused on individuals' cognitive and behavioural skills. The most intensively studied aspects are burnout and stress management, although well-being is widely understood in broader terms. According to a review by Buffer et al. (2013), work-related well-being is a comprehensive concept, which includes (besides occupational health and health behaviour), social and economic well-being and well-being connected to professional development, as well as both psychological and physical health. Moreover, each of these aspects are multidimensional. For example, psychological well-being encompasses self-esteem, autonomy, personal growth, sense of purpose in life, social support and mastery of environment (Jacobs et al., 2013).
As nurse leaders play key roles in staff retention and both the productivity and effectiveness of healthcare organizations, their performance should clearly be developed using evidence-based knowledge. Four previous reviews (Adams et al., 2019;Cummings et al., 2018;Long, 2020;Weberg, 2010) have examined effects of nurse leaders' different leadership styles on the nursing staff, their working environment and work-related well-being. Long's (2020) review of authentic leadership style showed that authentic leaders can promote newly qualified nurses' work-related well-being and retention. Adams et al. (2019) focused on the relationship between nurse managers' role and the well-being of ICU nurses and found that nurse managers' behaviours affected the well-being of their subordinates, through for example supportive behaviour, trust and inclusion in decision-making.
Although these reviews provided valuable insights, systematic reviews are needed to identify leadership styles that maximize nurses' work-related well-being and to provide recommendations based on the latest and best research evidence. Such recommendations are needed to support the development of organizational practices and effective healthcare environments and policy. Thus, this article presents a systematic review concentrating exclusively on nurse leaders' leadership styles and nurses' work-related well-being. The aim was to summarize empirical research on the relationships between them by addressing three research questions: 'Which leadership styles adopted by nurse leaders have been studied in connection with nurses' work-related well-being?', 'How was work-related well-being measured in those studies?' and 'How did the studied leadership styles reportedly affect nurses' work-related well-being?' 2 | METHODS

| Design
This systematic review of quantitative studies was designed and implemented in accordance with Cochrane Collaboration protocols (Higgins & Green, 2011) and the PRISMA statement (Moher et al., 2009, Figure 1).

| Search strategy and inclusion criteria
The CINAHL, Medic, SCOPUS and PubMed databases were systematically searched for relevant studies. The search strategies and terms were tailored to each database individually with guidance from a library-based information specialist. Searches were performed by combining search terms using the Boolean operators AND, OR and NOT. Searches were limited to peer-reviewed articles in English or F I G U R E 1 PRISMA flowchart  (Cummings et al., 2018) (Table 1).
The inclusion criteria were quantitative studies with experimental, quasi-experimental or descriptive designs on the relationships between nurses' work-related well-being and the support, leadership skills, or leadership style of nurse leaders.

| Search outcome and exclusion criteria
The search yielded 4408 hits: 1048, 2072, 1277 and 11 from the PubMed, CINAHL, SCOPUS and Medic databases, respectively.
After removing duplicates (362), 4046 articles remained for title and abstract review, which was performed by two researchers ( Figure 1).
Articles retrieved based on abstracts were excluded from further analysis, if they were not written in English or Finnish and/or irrelevant to the research questions. Reviews, editorials and discussion papers were also excluded. After this exclusion process, 90 articles remained for consideration. Two researchers read the full texts of these articles to evaluate their eligibility for the review, resulting in the exclusion of a further 77 articles. Articles were also excluded after examination of the full texts if they did not address the research questions, were not research articles, could not be retrieved, addressed employees other than nurses or multiple professions, but the findings were not separated by professions, or previously retrieved articles reported the same results. Researchers screened every article independently. The disagreements between the researchers were solved through consensus discussions. The third opinion was not needed.
The 13 articles remaining after this process were selected for inclusion, and their references were manually screened by two researchers to identify additional relevant articles. As a result, four further articles were included in the review ( Figure 1).

| Quality assessment
The final data consisted of 13 cross-sectional and 4 follow-up studies with surveys. They were assessed by two researchers with the checklist, Critical Appraisal of a Survey, developed for the survey studies (Center for Evidence-based Management, 2014). It included 12 criteria ( Table 2). The checklist did not include any guidance regarding rating the quality of the studies; therefore, the authors decided together the scale of ranking (Baatiema et al., 2017;Bahadori et al., 2020;Protogerou & Hagger, 2019). The researchers decided that if the study met over half of the criteria (7/12), it was accepted for the review. The quality was appraised satisfactory if the study met 7 or 8 of 12 criteria, and good if it met over 75% of the criteria (9 or 10/12). The quality of three studies was deemed satisfactory and others (n = 14) had good quality. All the studies that were included in the review addressed clearly focused questions using appropriate research methods, and the method used to choose subjects was described clearly. All the studies used representative samples and trustworthy measurement instruments. Satisfactory response rates were obtained in 14 of the studies, and the statistical significance of the results was assessed in all of them. However, confidence intervals were not reported in 11 of the articles, the minimum required sample size was only determined by preliminary statistical power analysis in six of the studies, and 16 of the articles did not address the possibility of confounding factors. All studies yielded results that were applicable to the authors' organization (Table 2).

| Data extraction and analysis
Specifying information of the publication, the purpose of the study, study subjects, study context, methodology and statistically significant outcomes reported in each included article were extracted to the matrix and are listed in Table 3. The articles were analysed by narrative synthesis (Popay et al., 2006;Ryan, 2013). First, each article was read through once to form an overview of its content. They were then read repeatedly to obtain deeper insight into their content. Descriptions of all identified leadership styles were reduced into codes by both researchers independently. These codes were compared, checked and completed together to reach all the essential expressions from the data. The codes were compared according to their similarities and differences. Similar expressions were grouped under the same theme and the themes were named according to associated content.
For example, in the study by Majeed and Fatima (2020) the exploitative leadership style was described as 'egoistic behaviour, manipulation and pressurizing'. This code was grouped under the theme 'nurse leaders' selfishness and nurses' bad treatment' and categorized under the core theme 'destructive'. Altogether three core themes were identified (destructive, supportive and relationally focused leadership styles). Then the measurements of work-related well-being and reported relationships (direct and indirect) between leadership styles and work-related well-being were examined. Due to the heterogeneity of the leadership styles and measurements of work-related wellbeing, further synthesis such as meta-analyses of the data was not possible (Higgins & Green, 2011).
Trust in the leader showed a positive relation with professional efficacy (.16, P < .01 in sample 1, .14, The standardized indirect effects of servant leadership on the three burnout factors vie the mediation of trust in the leader, and of servant leadership on intention to leave via the mediation of both trust in the leader and the cynicism factor of burnout, were statistically significant and equal to À.09 (P < .01), .14 (P < .01), À.16 (P < .01) and À.03 (P < .01), respectively, in sample 1 and equal to À.14 (P < .01), .13 (P < .01).
À.16 (P < .01) and .04 (P < .01) in sample 2 (Continues) Research, Author ( and transactional leadership styles and job stress were found, plus significant positive correlations between laissez-faire leadership style, job stress and anticipated turnover, as well as between job stress and anticipated turnover (all P < .001). A positive correlation between transformational leadership style and anticipated turnover, but negative correlation between transactional leadership style and anticipated turnover (r = À.28, P ≤ .001) were also found.  midwifes; and other health professionals such as physiotherapists or non-healthcare personnel (e.g. cleaning staff). Participants worked in elderly care facilities and acute or critical care, in public, private and non-profit maternity or governmental hospitals (Table 3).

| Supportive leadership styles and nurses' work-related well-being
Six studies described supportive leadership styles, such as supportive (Rodwell & Munro, 2013), transactional (Ebrahimzade et al., 2015Pishgooie et al., 2018;Sabbah et al., 2020), empowering (Bobbio et al., 2012) and resonant . Common recognized themes of these leadership styles were faith in employees' resources, organizational procedures targeting to enhance employees' capacities, desire to utilize resources fully in prevailing circumstances and acting as an example. Transactional leaders were described as task-oriented and to emphasize the roles of employees. They were said to concentrate on their relationships with their employees and promote interactions by building commitment to the organization.
Besides this, empowering and resonant leaders lead by example. They were described as participative in their decision-making. They coached, encouraged and informed their employees and showed them concern. They took account of the current situation, human resources, emotions and the surroundings (Bobbio et al., 2012;. These supportive leadership styles' associations with workrelated well-being were measured by four instruments: the MBI-GS in three studies (Bobbio et al., 2012;Ebrahimzade et al., 2015; (Table 4).

| Relationally focused leadership styles and nurses' work-related well-being
In total, 12 studies described relationally focused leadership styles, such as transformational (Ebrahimzade et al., 2015;Munir et al., 2012;Pishgooie et al., 2018;Sabbah et al., 2020), authentic (Laschinger et al., 2013Laschinger & Fida, 2014;Nelson et al., 2014;, servant (Bobbio & Manganelli, 2015) and ethical (Kaffashpoor & Sadeghian, 2020;McKenna & Jeske, 2021). These leadership styles differed from the leadership styles that we named supportive by the characteristics of the leader employee relationship and by the way leaders enhanced the growth of their employees and motivated them to involve in decision-making. Common identified themes of the relationally focused leadership styles included desire to form an equal and reciprocal relationship with employees, challenging employees to participate and value-driven behaviour. For example, transformational leaders were described as being visionary, intellectually stimulating and applying innovative methods to motivate their followers in problem-solving. They successfully coached groups to achieve their goals, encouraged their employees to participate, and inspired their self-confidence by giving them responsibilities and considering their personal differences (Ebrahimzade et al., 2015;Munir et al., 2012;Pishgooie et al., 2018;Sabbah et al., 2020). Ethical, authentic and servant leaders allowed employees to participate in decision-making, clarified expectations, communicated openly and clearly, and encouraged them to flourish and learn from mistakes.
They requested insights from employees before making important decisions and were described as honest, caring, fair, accountable, trustworthy and principled. They were aware of their own strengths and weaknesses, and personally integrated. (Bobbio & Manganelli, 2015;Kaffashpoor & Sadeghian, 2020;Laschinger et al., 2013;Laschinger & Fida, 2014;McKenna & Jeske, 2021;. In the studies on relationally focused leadership styles workrelated well-being was measured using eight instruments: the MBI-GS in six studies (Bobbio & Manganelli, 2015;Ebrahimzade et al., 2015;Laschinger et al., 2013Laschinger & Fida, 2014;McKenna & Jeske, 2021) and the Mental Health Index (MHI-5) in two studies (Laschinger & Fida, 2014;. The HSE was used by Pishgooie et al. (2018), a 5-item psychological well-being scale by Munir et al. (2012), and a four subjective well-being item scale by Kaffashpoor and Sadeghian (2020). In addition to these, the relationally focused leadership styles were measured by the Psychological Capital Questionnaire (Laschinger & Fida, 2014), the SF-12v2 (Sabbah et al., 2020) and the Psychological Well-being at Work scale, adapted from a scale by Masse et al. (Nelson et al., 2014). Transformational, ethical, servant and authentic leadership styles were found to have direct associations with work-related well-being. Transformational leadership reportedly had statistically significant direct negative relationships with burnout symptoms, including emotional exhaustion and depersonalization (Ebrahimzade et al., 2015) and a negative correlation with job stress (Pishgooie et al., 2018). Authentic leadership had a direct effect on psychological well-being according to Nelson et al. (2014) and a small negative impact on cynicism (Laschinger et al., 2013), whereas ethical leadership had been found to have direct effects on subjective wellbeing (Kaffashpoor & Sadeghian, 2020) and emotional exhaustion (McKenna & Jeske, 2021) (Table 4).
In addition to direct associations with work-related well-being, transformational, authentic and ethical leadership styles also reportedly had indirect associations. Work-life conflict mediated connections between transformational leadership and psychological wellbeing (Munir et al., 2012). Empowerment (Laschinger et al., 2013) and work climate (Nelson et al., 2014) mediated connections between authentic leadership and psychological well-being, including lower emotional exhaustion and cynicism, whereas job satisfaction was a mediator of effects of ethical leadership on subjective well-being (Kaffashpoor & Sadeghian, 2020). Recorded mediators of authentic leadership effects included emotional exhaustion on mental health problems (Laschinger & Fida, 2014), work life on burnout and mental health  and relational social capital via structural empowerment on mental health symptoms . Bobbio and Manganelli (2015) found that trust in the leader mediated significant standardized indirect effects of servant leadership in three burnout dimensions. Finally, McKenna and Jeske (2021) found that the mediator of ethical leadership effect on emotional exhaustion was decision authority (Table 4) Transformational leadership and its impact on employees' wellbeing has been studied extensively in several professional fields, yielding similar results to those discussed here (Gilbert et al., 2017;Jacobs et al., 2013;Kara et al., 2013;Kelloway et al., 2012;Nielsen et al., 2009;Sudha et al., 2016). For example, in hospitality, transformative leadership reportedly has a stronger positive effect on employees' work-related well-being than transactional leadership (Kara et al., 2013). Kelloway et al. (2012) found that non-transformational leadership styles were negatively connected with trust, which mediated effects on employees' psychological well-being. These results and those analysed in this review highlight the importance of evaluating leaders' leadership styles when considering nurses' work-related wellbeing. The available data suggest that nurse leaders should be capable of using supportive, empowering, resonant, transformational, transactional, authentic, ethical and servant leadership styles.
All the destructive leadership styles have negative connections to nurses' work-related well-being, and each of them were described in one article, except the laissez-faire style, which was addressed in three studies. This raises questions about why these leadership styles have been studied so rarely. The systematic review by Cummings et al. (2018) also identified two destructive leadership styles: dissonant leadership and management-by-exception with negative associations to nurses' work-related well-being based on two studies.
Thus, it is important to determine how widely unsatisfactory leadership styles are used, as well as how they affect nurses' work-related well-being and other nursing sensitive outcomes. More studies are needed to provide knowledge on characteristics of these destructive leadership styles, how they develop, their connections to adverse outcomes, and ways to prevent their negative effects. However, some relevant results have been presented, for example Lavoie-Tremblay et al. (2016) showed that abusive leadership styles negatively affect patient outcomes.
Work-related well-being has been mainly evaluated in terms of burnout, in keeping with previous findings of reviews by Awa et al. In the future, objective measures such as sick leave rates and productivity indicators should also be included in the study designs. Studies were cross-sectional or follow-up surveys and although many of them were based on sophisticated multivariate statistical analyses and results of the studies were consistent, the strength of the evidence remains low. Intervention and longitudinal studies are therefore needed to obtain stronger evidence regarding associations between nurse leaders' leadership styles and nurses' work-related well-being.
The studies should also be replicated in different settings. We need also research-based evidence regarding interventions' content and approaches that can fruitfully develop nurse leaders' leadership styles.
Although we have some evidence of interventions such as coaching, summits, mentoring or workshops for nurse leaders, more studies are needed to identify what kind of leadership interventions are the most effective and the study designs need to be stronger. It is also pivotal to acknowledge the contextuality of the leadership practices and the influence of the whole team and culture on the work-related wellbeing, not just the individual relationships between nurse leaders and nurses .
The results of our review of indirect effects of leadership styles on work-related well-being and the mediating factors underline the complexity of the focal phenomena. Many factors may interactively influence experiences of nurses' work-related well-being and the complexity requires further attention. Our review also showed that leadership styles can influence diverse other important variables, such as nurses' job satisfaction (Bobbio & Manganelli, 2015;Kaffashpoor & Sadeghian, 2020;Munir et al., 2012), incivility , empowerment (Laschinger et al., 2013, turnover (McKenna & Jeske, 2021;Pishgooie et al., 2018), early career burnout (Laschinger & Fida, 2014;Trepanier et al., 2019), affective commitment (Trepanier et al., 2019), psychological detachment from work (Majeed & Fatima, 2020), work climate (Nelson et al., 2014), worklife and the development of trustful relationships . Organizations should concentrate on creating structurally empowering work environments (Laschinger et al., 2013), trusting relationships and positive workplace environment  when developing leadership styles of their leaders. When these factors are developed in the interventions together with leadership styles, we can assume that the interactivity of the factors produce positive comprehensive effects on the work-related well-being. We need future studies to develop these many-sided interventions and to evaluate their effectiveness by objective measurements .
Appropriate leadership styles are essential for creating healthy work environments, promoting nurses' well-being, and avoiding high turnover. In addition to these nurse workforce outcomes, nurse leaders' performance influences patient outcomes (Goedhart et al., 2017;Lavoie-Tremblay et al., 2016;Wong et al., 2013). Healthcare organizations are complex systems and leaders must be comfortable using several different leadership styles in different situations. Leaders must also be aware of their own leadership styles and their effectiveness and the mediating factors in the work environment regarding employees' work-related well-being, and constantly seek to improve their own skills and work environment. This is greatly facilitated by the support of superiors. Leaders need more knowledge on how to identify the differences between the different leadership styles and how to apply supportive and relationally focused styles instead of destructive styles. They also need training on how to use different leadership styles in different situations. The training should be systematic, evidence-based and cover all levels of the organization. It should also provide a deep understanding of the complexity of the phenomena.

| Limitations
Several limitations of this study have already been highlighted, but some others should also be mentioned. The search process was conducted with an information specialist using database directories in efforts to ensure that the search was sufficiently systematic and extensive. The search terms and selection process have been described in detail above to allow repeatability. Several electronic databases were searched, and the results were complemented by reviewing reference lists of articles included in the final sample to minimize the likelihood of selection bias. The language selection criterion may have caused the exclusion of relevant studies published in languages other than English or Finnish. The grey literature was not taken into account in the review. This may have also increased the probability of bias when acquiring material to review. The reliability of the analysis was increased by using a matrix, in which the analysed articles are described in detail.

| CONCLUSION
This systematic review of quantitative studies clearly showed that nurse leaders' leadership styles significantly influence nurses' workrelated well-being. In total, 14 of the reviewed studies focused on 12 leadership styles with positive impacts on nurses. More research is required on unrecommended leadership styles, their prevalence and their impact on nurses' work-related well-being. Work-related wellbeing was mainly measured and defined in terms of burnout; this narrow definition prevents a holistic analysis of the relationship between leadership styles and work-related well-being. The strength of the evidence in this field appears to be low; intervention studies are needed to get stronger evidence regarding nurse leaders' leadership styles and their direct and indirect impacts on nurses' work-related wellbeing to inform healthcare policy and organizations, educators, and researchers. In the developing of intervention studies on work-related well-being, the results of the indirect effects and the mediating factors of the leadership styles should be acknowledged. Because nurse leaders' leadership styles affect nurses' work-related well-being, systematic evaluation of these styles in organizations is important. Organizations should invest in nurse leaders' education. Results of this review could be used when developing work environments, planning and implementing leadership training.